EP2647023A1

EP2647023A1 - Electrical switch element of the smd type

Info

Publication number: EP2647023A1
Application number: EP11791283.2A
Authority: EP
Inventors: Hanna Lehmann; Markus Fuchser
Original assignee: EAO HOLDING AG
Current assignee: EAO HOLDING AG
Priority date: 2010-12-03
Filing date: 2011-12-02
Publication date: 2013-10-09
Also published as: CN103403828A; US20130248340A1; WO2012072809A1

Abstract

The invention relates to an electrical switch element of the SMD type having a body (11, 12) comprising the switch element, at least two contact surfaces (22, 24), which are provided on the lower face (42) of the body (11, 12) for SMD attachment, and an actuating element (3, 5, 6, 39), which is provided on the side opposite the lower face (42) and is movably connected to the body (11, 12) for a movement component in accordance with the longitudinal axis (43) of the switch element. An electrically conducting connection is established between the contacts (22, 24) via a switch contact (10), which can be closed with the relative movement of the actuating element (3, 5, 6, 39) to the switch contact (10). The body (11, 12) has a lower part (12), which comprises the two contact surfaces (22, 24) and the switch contact (10), and an upper part (11), which comprises the actuating element (3, 5, 6, 39). The lower part (12) and upper part (11) are to be connected via complementary latching elements (18, 19). The lower part (12) can thus be produced from a plastic material resistant to the heat of SMD soldering, while the upper part (12), which is produced from conventional materials, is placed on the lower part (12) only after soldering and completes the switch or push-button.

Description

TITLE

Electrical switching element of the SMD type

TECHNICAL AREA

The present invention relates to an electrical switching element of the SMD type according to the preamble of claim 1, in particular an electric illuminated pushbutton of the SMD type.

STATE OF THE ART

The SMD manufacturing process, which stands for Surface Mounted Device, is a circuit board assembly process that has several advantages. If there is computerized equipment, the electrical elements to be equipped can be soldered directly to the surface of a printed circuit board. Since no parts of the electrical components through the circuit board punched through, it is advantageous that both sides of the circuit board can be equipped with circuits.

From DE 10 2006 040 803 an optical touch switch is known, which is arranged as an SMD component on a carrier having SMS contacts, which can then be contacted electrically with the conductor track of a printed circuit board.

Thus, the assembly cost when applying a switch on a circuit board can be reduced. The four lateral SMD contacts allow a contacting of the plate-shaped optical switching element on a printed circuit board. The switch is protected by a cover against direct contact and works as an optical touch switch. SUMMARY OF THE INVENTION Based on this prior art, it is an object of the invention to specify an SMD-type electrical switching element of the type mentioned initially, which is designed as a pressure switch. Another object of the invention is to provide an illuminated SMD push button. Another other object of the present invention is to increase the reliability of such a button.

This object is achieved according to the invention with the features of claim 1. An SMD-type electrical switching element has a body comprising the switching element, at least two contact surfaces provided on the underside of the body for SMD mounting, and an actuator provided on the opposite side of the underside corresponding to the body for a movement amount the longitudinal axis of the switching element is movably connected. In this case, an electrically conductive connection between the contacts is now made via a switching contact which can be closed to the switching contact with the relative movement of the actuating element, in particular a relative movement along the longitudinal axis of the switching element, ie the central axis perpendicular to the printed circuit board. The body now has a lower part, which has the two contact surfaces and the switching contact, and an upper part, which comprises the actuating element. Lower part and upper part are to be connected via complementary locking elements. Thus, the lower part can be made of a heat resistant to the heat of an SMD solder resisting plastic, while the upper part, made of conventional materials, after soldering is first placed on the base and completes the switch or push button.

The further object is achieved with the features of claim 7. Such a switching element has an actuating element with an actuating nose, with which by the said relative movement of the actuating element to the switching contact Contacts are closed. Advantageously, the switching contact is a resilient tongue, which is fixedly connected to a contact, for example, soldered, and has a projecting into the range of movement of the actuating nose area, which can therefore be pushed away. In this case, the switching contact is an elongated spring, which is divided by at least one longitudinal slot in at least two parallel resilient blades. In the case of two or more longitudinal slots, these slots are at least partially different in length from each other, all slots penetrating at least the contact area between the tongue and the mating contact, at least one projecting into the end area of the resilient lamellae.

Further embodiments are given in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will be described below with reference to the drawings, which are given by way of illustration only and are not to be interpreted as limiting. 1 shows a partially sectioned cross-sectional view of two pushbuttons arranged side by side on a printed circuit board according to an embodiment of the invention,

2 is a perspective view of a pressure switch of FIG. 1,

3 is an exploded view of the switch according to FIG. 2,

Fig. 4 is a partially sectioned perspective view of the lower part of

Push-button according to FIG. 2, with the feature of redundant contact,

Fig. 5 is a partially sectioned plan view of the lower part of FIG. 4, and FIG. 6 is a partially sectioned cross-sectional view of the on a

Printed circuit board mounted push button. DESCRIPTION OF PREFERRED EMBODIMENTS

Fig. 1 shows a partially sectioned cross-sectional view of two side by side arranged on a printed circuit board push-buttons 1, which are mounted on a printed circuit board 2, wherein the actuating hood 3 of the push-button 1 protrude through a front panel 4. The SMD type electrical switching element according to the invention is an electrically illuminated pushbutton or pushbutton. The illustration is schematic with respect to the printed circuit board 2. Usually, a printed circuit board 2 is equipped with a corresponding circuit in a control panel, which are switchable via various actuators, in particular the push-button 1. The printed circuit board 2 is arranged in a frame below the front panel 4 of a control panel, wherein the operating covers 3 of the controls protrude to the front panel 4. On the left side of Fig. 1, the push-button 1 is not actuated, so the Rontakt not closed, while in the pressed push-button 1 on the right side of the representation of the contact is closed.

The structure of the pushbutton 1 will now be described in more detail in connection with the perspective view of FIG. 2 and the exploded view of FIG. 3. Instead of a pushbutton 1, which latches on the releasable locking lugs 15 and 16 and thus defines an ON and an OFF position, it is also possible that it is a pure switch button, which goes back to the starting position after contacting, the Lighting should be designed differently due to the greater distance from the light guide 13 to the diffuser 5.

The push-button 1 consists of several elements of the operation, which are prefabricated as a unit and include as a protruding element, the pressure hood 3. Advantageously, the pressure hood 3 is already in several parts and consists of a transparent pressure hood 3 per se, under which a likewise transparent diffuser cap 5 is arranged. This advantageous double arrangement allows the insertion of labeling films between the pressure hood 3 and the diffuser 5 or for example a direct laser marking of the surface of the diffuser 5, which is then protected against abrasion during use by the pressure hood 3. Basically Here also a one-piece design possible. The print 3 is clipped onto a guide frame 6. This embodiment of the connection of pressure hood 3 and diffuser 5 is basically known and could also be produced by gluing or welding. The guide frame 6 has a plurality of downwardly from the pressure hood 3 removing guide profiles, one of which is provided with the reference numeral 7. A corresponding profile 8 of the guide frame 6 has been designated by the reference numeral 8.

Furthermore, the guide frames 7 forming a closed frame, as is apparent from the sectional top view of FIG. 5, comprise an actuating wall 9 with which the contact tongue 10 of the pushbutton 1 can be switched. This actuating part of the switch 1 moves in particular along its main axis 43 relative to the upper part 11 of the switch and the lower part 12 of the switch. These actuators 3, 6, 9 are advantageously clipped into the upper part 11 of the switch, so that the said longitudinal movement between the upper part 11 and the actuators 3 and 6 of the pushbutton is possible, but these elements before assembly and after assembly in the Do not fall apart. Integrated in this framework, ie in particular connected to the upper part 11, the light guide 13, which is centrally inserted in the upper part 11 and the guide frame 6. The guide frame 6 can be hooked in via the nose 16 located in a recess in and under corresponding lugs 15 of the upper part 11.

The light guide 13 engages with lateral grooves 14 in corresponding connection tabs of the upper part 11 a. For this purpose, corresponding recesses 28 are provided in the guide frame 6, so that the guide frame 6 via the light guide 13 and between its connection to the upper part 11 longitudinal, ie along the main axis 43 of the probe, is movable.

Thus, after the operation of the switch, the guide frame 6 with the pressure hood 3 back to its initial position shown in FIG. 1, two springs 17 are provided, which are supported on a provided in the upper part 11 base plate and opposite in the upper part 11 at a lower edge of the guide frame 6 find their abutment. The lower part 12 of the push-button 1 has four locking lugs 18. The locking lugs 18 are provided in the side surfaces of the lower part 12 respectively on opposite sides. In each case two are arranged near the corners. The locking lugs 18 extend upwards in the direction from which the upper part 11 can be placed and they can be inserted into corresponding Aufhahmeöffhungen 19 of the upper part 11 and then latched. Thus, the lower part 12 and the upper part 11 with inserted and independently latched operating part 3, 6, 13 are connected in a functional unit.

The lower part 12 has an extending into the upper part 11 contact carrier 20, which may for example be integrally formed and made of the same material with this. On the contact carrier 20, the contact 23 terminates in a longitudinal edge of the extending contact strip, on which a free end of the contact tongue 10 is arranged fixed, in particular soldered. The other end of the contact tongue 10 with the reference numeral 40 extends on the side facing the housing outside of the contact carrier 20. It is arranged at a lateral distance from a mating contact 22 which extends in the contact carrier 20 substantially in the main plane and thus with its broad Surface of the contact tongue 10 and a spring portion 35 is arranged opposite. The mating contact 22 then has on the outside of the lower part 12 via a surface which is provided for contacting with the printed circuit board 2. In addition, it can be seen in FIG. 3 that the contact 23 can be connected to the printed circuit board 2 via a connection in the interior of the housing via the contact plate 24. The contact plate is placed behind a shoulder down and is like the corresponding contact plate 22 on the bottom 42 of the base 12, for example in a corresponding recess. In particular, these contact surfaces with the bottom 42 of the base 12 close flush.

For the invention of the illustrated exemplary embodiment, the illustrated course of the arrangement of the contacts is advantageous. However, it is essential at first only the integration of the SMD-capable contacts 22 and 24 on the lower part 12, wherein a part of the contact chain 24-23-20-35-22, namely the contact 35 by the operating lug 39 of the upper part 11 can be triggered. In Figs. 2 and 4 are also positioning feet 25 shown, of which in particular the number of two can be provided at diametrically opposite corners of the bottom 42 of the base 12. These protrude then, as shown in FIG. 6, preferably in provided by component side of the pushbutton 1 blind holes 26 in the circuit board 2. This positioning aid is particularly useful in a manual assembly of the circuit board 2 with the bases 12, while in an automated SMD Placement these leading positioning feet 25 are not necessary and therefore can be omitted. They thus increase the applicability of the push-button 1 in several embodiments for different needs of customers.

An illuminated SMD button 1 according to the invention has the advantage that an internal cavity or opening 29 is present through the frame-shaped shape of the lower part 12, in which one, two or three LEDs 30 on the circuit board 2, in particular LED SMDs equipped can be. In this case, the light guide 13 is positioned with respect to the upper part 11, and thus determined via the direct connection to the lower part 12 also with respect to the printed circuit board 2 in the position that the underside 31 of the light guide 13, preferably a smooth rectangular surface 31st is arranged in the smallest possible distance of 2 to 3 mm above the upper edge of the SMD-connected LEDs 30 is arranged. This can be ensured with the advantageously curved, here plano-convex upper mold 32, which cooperates with the plano-concave diffuser hood 5, a good light output can be ensured.

Manufacturing technology is important the division of the housing of the push-button 1 in a SMD-mountable lower part 12 and a the operating part 5, 6, 8 and the light guide 13 comprehensive upper part 11th

Essential in such an illuminated push-button 1 is the well-adjusted arrangement of the fixed relative to the upper housing part 11 light guide 13 and the leadership of the hatch 3 with respect to this upper housing part 11. This increased accuracy in the manufacture of the components is sensitive to the temperature and the upper housing part 11 should therefore not be exposed to elevated temperatures, as is usually the case with SMD soldering. Therefore, this component 11 of the push button 1 separated from the component 12, which together with the preferably integrated in it contact 20, 22, 23 and 24 in SMD construction on the circuit board 2 is soldered. For this, the lower part 12 consists of a high-temperature plastic - possibly quite the opposite of the upper part 11, are used for conventional plastics - so that the lower part 12 does not warp in the heat during the SMD attachment process in its dimensions. This is then after this attachment step, the upper part 11 can be clipped to assemble the finished push-button 1.

A high-temperature plastic for the lower part 12 is suitable to withstand the temperatures occurring during an SMD soldering over the Lötverfahrensdauer and remain dimensionally stable. Depending on the method and soldering oven used, temperatures of 180 to 280 degrees Celsius in particular may occur over a period of 1 to 2 minutes. Heat stable means that the lower part does not change or changes only insignificantly compared to its original shape prior to soldering, ie has the same physical shape physically physically the same and advantageously also has no chemically altered properties.

Fig. 5 shows in the partially sectioned plan view well some elements of the drawings described above, in particular the placement of the springs 17 on corresponding cylinder 33 and the three guide profiles, the laterally projecting profiles 7 and the profile groove 8, in which a nose 34 of the upper part 12 protrudes. The profile 7 is opposite to a complementary recess 41 in the wall of the upper part 11, which dilutes the wall thickness. It should be noted that if the upper part 11 becomes warm with respect to the guide frame 6, ie would have a significant temperature difference, this would impair the guiding properties between the sliding surfaces 7-41 and 8-34. Through the elements 7 and 8 results in a Dreipunktführang against the inner wall of the upper housing part 11 with a low-noise feel after assembly.

Furthermore, it can be seen that the base of the light guide 13 occupies the essential part of the interior of the upper part 11 and thus with its opposite the lower surface 31 tapered shape covers the entire cavity 29 of the lower part 12 and thus with respect to the exact positioning of a , two or three LEDs 30 between the SMD attachment points for the push-button 1 with respect to the light pipe is insensitive. Instead of the cylinder 33 with a counter surface in the region of the example presenting as a collar bottom 27 between guide frame 6 and diffuser 5, as counter-pressure surfaces for compression springs 17 also tension springs can be used, which are then hooked to corresponding stops on top 12 and frame 6.

Such a switch can be used in particular for example for a video desk use and the circuit board 2 is then back equipped without restriction with other components.

It can therefore be accommodated in the same place more functions. The lower part 12 of the push-button 1 is fixed for example by means of a reflow soldering process on the circuit board 2. The light sources 30 are advantageously SMD LEDs 30, which are fastened centrally between the contacts 22, 24 of the push button 1.

The lower part or contact carrier 12 is on the circuit board 2 by hand (if the lugs 25 are provided) or automatically positioned and then soldered by means of a soldering process in the heating furnace to the circuit board 2. Subsequently, after cooling, the key top 11 can be placed on the key base or contact carrier 12 and latched by means of the lugs 18 in the recesses 19.

Another object of the present invention is to ensure the operability of the switching system over a very large number of several hundred thousand switching operations. The illustrated pushbutton is not a fully enclosed system, so over time contaminants may enter the housing via the top 11 and base 12 and interfere with the operation of the switching system. In principle, the contact spring 10 is switched by the operating wall 9 of the frame 6 and there in particular by the recognizable in Fig. 3 contact lug 39 against the mating contact 22 in a traditional manner. This contact tongue 10 has for a projecting in the direction of the mating contact 22 spring portion 35, while for the §§Kontaktierung with the contact nose 39 an opposite projection 36 is provided. The contact tongue 10 is now executed slotted in the illustrated embodiment on the elements 35 and 36 away. In the illustrated embodiment, there are three extending in the longitudinal direction of the spring 35 and recesses 36 slots 37, which divide the contact tongue 10 in four lamellae 38. Now, if an impurity on the or under the contact tongue 10 reaches a total, it is very likely that due to the size of the penetrated elements these span only a portion of the width of the tongue and thus one or more slats can still be actuated by the operating lug 39 ,

From Fig. 4 also shows that the length of the slots 37 is different. In an advantageous embodiment with at least three fins 38 and thus two or more slots 37, it has been found in experiments that it is very advantageous if the slots 37 have a different length, so that only one slot 37 ends in the end region 40 of the contact tongue 10 and the other slots 37 are set back and thus form a larger solid material of the resilient contact tongue 10 at the reed tip 40. As a result, the number of actuation cycles can be increased by a factor of 5 to 10 before material fatigue occurs with respect to the case when all slat slots 37 are of equal length. In particular, the louver slots 37 extend beyond the spring-tab-forming portion 35 opposite the contact 22, but do not all pass beyond the counter-elevation 36 for operation by the tab 39.

LIST OF REFERENCE NUMBERS

Pushbutton 23 contact

PCB 24 contact

Pressure hood 25 Positioning

Front panel 26 blind hole

Diffuser 27 bottom

Guide frame 28 recess

Profile 29 Breakthrough

Profile groove 30 LED

Actuating groove 31 base

Contact tongue 32 convex lens shape

Top 33 cylinders

Lower part / contact carrier 34 nose

Optical fiber 35 spring

Groove 36 recess

Nose 37 slot

Nose 38 lamella

Spring 39 contact nose

Latch 40 end area

Aufhahmeöff 41 recess

Contact carrier 42 base

Contact surface 43 longitudinal axis

countercontact

Claims

An electrical switching element of the SMD type, comprising a body comprising the switching element (11, 12), with at least two contact surfaces (22, 24) provided on the underside (42) of the body (11, 12) for SMD attachment are, with an on the underside (42) opposite side provided actuator (3, 5, 6, 39) which is movably connected to the body (11, 12) for a movement proportion corresponding to the longitudinal axis (43) of the switching element, with a switching contact (10) designed to produce an electrically conductive connection between the contacts (22, 24), which can be closed with the relative movement of the actuating element (3, 5, 6, 39) to the switching contact (10), characterized in that Body (11, 12) via a lower part (12), which has the two contact surfaces (22, 24) and the switching contact (10), and an upper part (11), which the actuating element (3, 5, 6, 39 ), and that lower part (12) u nd upper part (11) via complementary latching elements (18, 19) for connecting the lower part (12) with the upper part (11) have.

Switching element according to claim 1, characterized in that the lower part (12) consists of a heat-stable plastic compared to the occurring during an SMD soldering over the Lötverfahrensdauer temperatures, in particular from 180 to 280 degrees Celsius over a period of 1 to 2 minutes.

Switching element according to claim 1 or 2, characterized in that the lower part (12) has a through the side walls of the lower part (12) bordered central opening (29).

4. switching element according to claim 3, characterized in that the with the

Upper part (11) connected actuating element (3, 5, 6) via a with the Obeerteil (11) connected to the central optical fiber (13), the composite switching element at a predetermined distance with its lower edge (31) opposite the bottom (42) of the lower part (12). Switching element according to claim 3 or 4, characterized in that the actuating element (3, 5, 6) has a guide frame (6) projecting into the upper part (11) which, viewed in the longitudinal direction of the switching element, has complementary guide profiles (7, 41; , 34), in particular via recesses and complementary profile noses.

Switching element according to claim 3, 4 or 5, characterized in that the upper part has at least one, advantageously two, spring supports (33) on which are supported springs (17) which abut against an abutment on the underside (27) of the actuating element ( 3, 5, 6).

Switching element according to the preamble of claim 1 or according to one of claims 1 to 6, characterized in that the actuating element (3, 5, 6) has an actuating nose (39) with which by said relative movement of the actuating element (3, 5, 6, 39) to the switching contact (10) the contacts (22, 24) are closable.

Switching element according to claim 7, characterized in that the switching contact (10) via a resilient tongue (10) which is connected to a contact (22) and via a in the range of movement of the actuating lug

(39) projecting area (36).

Switching element according to claim 7 or 8, characterized in that the switching contact is an elongated spring, which is divided by at least one longitudinal slot (37) in at least two parallel resilient laminations (35).

Switching element according to claim 9, characterized in that at least two longitudinal slots (37) are provided, which are of different lengths, wherein all slots (37) at least the contact region (35) between the tongue (10) and counter-contact (22), wherein at least one in the end area

(40) of the resilient blades (35) protrudes.